Removal Method and Removal Apparatus for Entrained Air in Coating Fluid

ABSTRACT

The present invention has as an object to render a photochromic coating layer free from air bubbles and obtain a uniform layer without film thickness unevenness in the coating layer. In the prevent invention, entrained air in a coating fluid stored in a vessel of a coating unit comprising the vessel, a check valve for preventing back-flow of the coating fluid connected to the vessel, and optionally an ejection nozzle connected to the check valve; air existing inside of the check valve; and optionally air existing inside of the ejection nozzle are removed by plugging an outlet of the coating fluid existing downstream of the check valve and then rotating the coating unit on an axis of the vessel and orbiting the coating unit on a revolution axis simultaneously.

TECHNICAL FIELD

This invention relates to a method for removing air entrained in acoating fluid stored in a container called a coating unit, and a removalapparatus for use in its removal.

BACKGROUND ART

Among materials which change in color when exposed to light is aphotochromic material. The photochromic substance has the property thatits structure reversibly changes according to the presence or absence ofultraviolet radiation to change in absorption spectrum. This propertyresults from the nature that when an isomer is irradiated with light ofa particular wavelength, the single chemical substance, under the actionof light, reversibly produces an isomer having a different absorptionspectrum. The resulting different isomer is restored to the color of theoriginal isomer by heat or light of a different wavelength.

Photochromic spectacles utilize the above nature of the photochromicmaterial for lenses. In an outdoor environment exposed to lightincluding ultraviolet radiation, such as sunlight, the lenses arerapidly colored to function as sunglasses. In an indoor environmentwithout exposure to light, the lenses fade to function as ordinarytransparent spectacles.

Known methods for producing a lens having photochromic property includea method of impregnating the surface of a non-photochromic lens with aphotochromic coating fluid; a method which comprises dissolving aphotochromic coating fluid in a monomer, and polymerizing the solutionto obtain a photochromic lens directly; and a method comprisingproviding a layer having photochromic property on the surface of a lenswith the use of a coating agent containing a photochromic compound(namely, a coating method). An apparatus for forming a layer havingphotochromic property on a lens by the coating method is disclosed.

In the above-described coating method, when the photochromic coatingfluid is supplied onto the lens, the photochromic fluid is ejected fromthe nozzle of a vessel containing the photochromic fluid to the surfaceof the lens to form a coating layer on the surface of the lens.

However, the photochromic fluid has viscosity, so that if air isentrained in the fluid, air bubbles are formed in the resulting coatinglayer. The nozzle of the vessel is provided with a check valve forpreventing fluid dripping. In this case, air may be incorporated in thenozzle at the start of operation, thus requiring that air in the nozzlebe discharged outside before start of the operation. For this purpose,air purge of the nozzle is performed using the coating fluid. This posesthe problem of a great expenditure, because the photochromic fluid isexpensive.

The present invention has been accomplished in the light of suchcircumstances. It is an object of the invention to provide a removalmethod for entrained air in a coating nozzle, and a coating apparatus,the removal method and the coating apparatus unable to form an uniformphotochromic coating film without voids and thickness unevenness.

In connection with the present invention, technologies such as thetechnology described in Japanese Unexamined Patent Publication No.2000-334369 concerning with an apparatus which can coat a plurality oflenses continuously, the technology described in Japanese UnexaminedPatent Publication No. 2005-013873 concerning with an apparatus equippedwith an auxiliary mechanism for spreading a coating fluid on a lens withthe use of a flexible film, and the technology described in JapaneseUnexamined Patent Publication No. 2005-218994 concerning with anapparatus which adjusts the rotational state of a lens according to theshape of the lens or the viscosity of a coating fluid are available.

DISCLOSURE OF THE INVENTION

The method for removing air from a coating fluid containing entrainedair according to the present invention (hereinafter referred to as theremoval method for entrained air according to the present invention)comprising the steps of:

(A) preparing a coating unit comprising a cylindrical vessel storing thecoating fluid and a check valve for preventing back-flow of the coatingfluid connecting with the vessel;

(B) plugging an outlet of the coating fluid existing downstream of thecheck valve; and

(C) rotating the coating unit on an axis of the vessel and orbiting thecoating unit on a revolution axis simultaneously whereby introducing thecoating fluid into the check valve, discharging air resided inside ofthe check valve toward the vessel, and further removing air incorporatedin the coating fluid from the coating fluid.

In the present invention described above, the coating unit prepared inthe step (A) further can contain an ejection nozzle for ejecting thecoating fluid connecting with the check valve. In such a case, theplugging in the step (B) is carried out by plugging an outlet of theejection nozzle, and the coating fluid is introduced into the checkvalve and the ejection nozzle, and the air inside the check valve andthe air inside the ejection nozzle are discharged toward the vessel inthe step (C). Meanwhile, the air inside the ejection nozzle is notdischarged when the deaeration was carried out using the coating unitwithout the ejection nozzle and the ejection nozzle was loaded after thedeaeration.

In the present invention, the rotational speed of revolution of thecoating unit is preferably set such that the speed in the late stage ofa rotating operation is rendered higher than the speed in the earlystage of the rotating operation.

In the present invention, the coating fluid can be a photochromiccoating fluid to be coated on the surface of spectacles.

The removal apparatus for entrained air in a coating fluid according tothe present invention (hereinafter referred to as the removal apparatusfor entrained air or deaeration apparatus of the present invention)comprises a casing which can rotate on a rotation axis and also canorbit on revolution axis, and a coating unit comprising a cylindricalvessel accommodating a coating fluid inside, a check valve forpreventing back-flow of the coating fluid connecting the vessel and alid for plugging an outlet of the coating fluid existing downstream ofthe check valve; wherein

the rotation axis being located, with respect to the revolution axis,outwardly and downwardly in a circumferential direction of an orbital onthe revolution axis,

the coating unit being supported by the casing detachably such that thelid of the coating unit is located below, and

the coating unit being rotated on the rotation axis and being orbit onthe revolution axis simultaneously with the casing, to discharge airresided inside of the check valve toward the vessel, and further toremove air incorporated in the coating fluid.

The coating fluid used in the present invention can be a photochromiccoating fluid to be coated on the surface of spectacles.

In the present invention, a flange facing outward can be formed on theperiphery of the vessel, and the flange can be detachably mounted on thecasing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a photochromic coating apparatus described inan embodiment of the present invention.

FIG. 2 is a front view of the photochromic coating apparatus of FIG. 1.

FIG. 3 is a longitudinal (in the up-and-down direction; the same applieshereinafter) sectional view of a lens support device in the photochromiccoating apparatus of FIG. 1.

FIG. 4 is a front view of a coating unit support device in thephotochromic coating apparatus of FIG. 1.

FIG. 5 is a side view of the coating unit support device of FIG. 4.

FIG. 6 is a longitudinal sectional view of a coating unit supported bythe photochromic coating apparatus of FIG. 4.

FIG. 7A is a longitudinal sectional view, before deaeration, of a fluiddrip preventing valve (the check valve) mounted in the vicinity of anoutlet of the coating unit of FIG. 6. FIG. 7B is a longitudinalsectional view, after deaeration, of the fluid drip preventing valve.

FIG. 8 is a schematic view of a removal apparatus according to theembodiment of the present invention.

FIG. 9 is a sectional view of a state in which the coating unit of FIG.6 is supported by the casing.

FIG. 10 is a plan view of a lens height measuring sensor in thephotochromic coating apparatus of FIG. 1.

FIG. 11 is a side view of the lens height measuring sensor of FIG. 10.

FIG. 12 is a plan view of a coating film uniformizing device in thephotochromic coating apparatus of FIG. 1.

FIG. 13 is a plan view of the coating film uniformizing device of FIG.12.

FIG. 14 is a side view of a UV device in the photochromic coatingapparatus of FIG. 1.

FIG. 15 is an enlarged side view of the UV device of FIG. 14.

FIG. 16 is a plan view of a movable fluid receiving device in thephotochromic coating apparatus of FIG. 1.

FIG. 17 is a side view of the movable fluid receiving device of FIG. 16.

FIG. 18 is a flowchart of the coating apparatus for a lens.

FIG. 19A is a sectional view of a state in which the height of the lensis measured with laser light from the lens height measuring sensor shownin FIG. 10. FIG. 19B is a sectional view for illustrating how to lead tothe edge position of the lens.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of a removal method for entrained air in a coating fluidaccording to the present invention will now be described with referenceto the accompanying drawings.

FIGS. 1 and 2 show a photochromic coating apparatus for coating aphotochromic fluid onto a lens under automatic control. The lower sideof the photochromic coating apparatus in FIG. 1 is the front side of theapparatus (in the Y-axis direction), and the right-to-left side of theapparatus is in the lateral direction (X-axis direction).

A photochromic coating apparatus 1 has a lens support device 3, acoating unit support device 4, a lens height measuring sensor 6, acoating film uniformizing device 7, a UV device 8, and a movable fluidreceiving device 9 provided on a base stand 2.

As shown in FIG. 3, the lens support device 3 is provided in a nearlycentral portion of the base stand 2, and has a circular pedestal 31formed to protrude upward from the base stand 2. A guide member 32 isprovided inwardly of the base stand 2, and a Z-axis ball screw 33 havingan axis pointing in the up-and-down (vertical) direction is provided onthe guide member 32. The Z-axis ball screw 33 has an upper end portionrotatably mounted on the guide member 32, and a lower end portionmounted on a servo motor 34. A Z-axis ball nut 36 mounted on a lenssupport member 35 is screwed to the Z-axis ball screw 33. As the Z-axisball screw 33 is rotated, the lens support member 35 can move upward anddownward along the Z-axis ball screw 33. A servo motor 37 is fixed to alower portion of the lens support member 35, and a rotating shaft 38extending upward is mounted on the servo motor 37. The rotating shaft 38passes through a hole 31 a formed in the circular pedestal, and a lenssupport stand 39 is mounted on a front end portion of the rotating shaft38. When the servo motor 37 is rotated, the lens support stand 39rotates about the rotating shaft 38.

FIGS. 4 and 5 show the coating unit support device 4. In the coatingunit support device 4, an air slide table 11 is provided on the basestand 2, and a slide block 12 is fitted onto the slide table 11 to beslidable in the lateral direction of the photochromic coating apparatus1. The slide block 12 is slidable by a rodless cylinder, and the rodlesscylinder of the air type, chain type, magnet type, slit type, or wiretype can be applied (the same is true of rodless cylinders to follow).

A support arm 13 extending toward the front side of the base stand 2 ismounted on an upper end portion of the slide block 12 erected upward,and a coating unit 21 is supported by the support arm 13. The supportarm 13 is mounted such that the support angle of the coating unit 21 canbe changed about a pivot shaft 14 as an axis. That is, as shown in FIG.4, the support arm 13 can support the coating unit 21 in an uprightposture, or in an inclined state as indicated by imaginary lines. Thecoating unit 21 can be moved to directly above the center of a lens 10by the lateral slide of the slide block 12 on the air slide table 11.

As shown in FIG. 6, the coating unit 21 is equipped with a vessel 22, acheck valve (a fluid drip preventing valve) 23, and a nozzle 24. Acoating fluid is contained in the vessel 22, the upper end of the checkvalve 23 is detachably connected to a lower portion of the vessel 22,and the nozzle 24 is detachably connected to the lower end of the checkvalve 23.

As shown in FIGS. 7A, 7B, the check valve 23 has a first small-diameterportion 23 a on its upper end side connected to the vessel 22, alarge-diameter portion 23 b at its center, and a second small-diameterportion 23 c at the leading end side thereof. A valve seat 23 d, where acushioning material 23 e such as an O-ring is disposed, is formed at theboundary between the first small-diameter portion 23 a and thelarge-diameter portion 23 b. A valve ball 25 of a spherical shape isdisposed in the large-diameter portion 23 b, and a spring 26 is disposedin a compressed state between the valve ball 25 and the secondsmall-diameter portion 23 c.

A plunger 27 is disposed inside the vessel 22, and when a compressionsource (N2) connected to piping 22 b imposes a load, the plunger 27presses the coating fluid to open the valve composed of the valve seat23 d and the valve ball 25. In this manner, the valve ball 25 is urgedagainst the valve seat 23 d by the spring 26 to restrain the flow of thecoating fluid from the nozzle 24 toward the vessel 22. On the otherhand, when the valve ball 25 is pressed in opposition to the force ofthe spring 26, the flow of the coating fluid from the vessel 22 towardthe nozzle 24 is allowed.

An explanation will be offered for a removal apparatus 15 according tothe present invention for removing air (air bubbles) contained in thecoating fluid accommodated in the coating unit 21.

The removal apparatus 15 shown in FIG. 8 is provided separately from thephotochromic coating apparatus 1. Before the coating unit 21 is set inthe coating unit support device 4, deaeration treatment is performed bythe removal apparatus 15. The removal apparatus 15 is provided with arotating body 16, and the rotating body 16 can be rotated on an axis ofrotation (a revolution axis) 17. A casing 28 for supporting the coatingunit 21, as shown in FIG. 9, is arranged at a position remote from thecenter of the rotating body 16. A hole 28 a is formed in a centralportion of the casing 28, and the coating unit 21 can be detachablymounted in the hole 28 a. An annular boss portion 28 b is formed on theupper surface of the casing 28 above the hole 28 a, and a rubber packing22 a is mounted on the boss portion 28 b by screws 29. The rubberpacking 22 a is mounted to suppress the freewheeling of the vessel 22 ofthe coating unit 21 by making contact with the periphery of the vessel22 when the coating unit 21 is rotated by the removal apparatus 15. AnO-ring 30 as a cushioning material is disposed at the bottom of the hole28 a into which the coating unit 21 is inserted.

The coating unit 21 has an axis (a rotation axis) 18 inclined in theup-and-down direction within the casing 28. A lower portion of thecoating unit 21 is directed toward the outer periphery of the rotatingbody 16, while an upper portion of the coating unit 21 is directedtoward the upper side of the axis of rotation (the revolution axis) 17of the rotating body 16. The ejection nozzle 24 is provided at a leadingend portion of the coating unit 21, and a lid 24 a is mounted on theoutlet of the ejection nozzle 24.

The casing 28 is adapted to be rotated by a drive motor 19 on the axis(the rotation axis) 18 together with the coating unit 21. The rotatingbody 16 is arranged to be rotated or orbited by a drive motor 20 on theaxis of rotation (the revolution axis) 17. The coating unit 21 can doorbital motion or revolution which means orbiting on a revolution axison the revolution axis 17, and can rotate on the rotation axis 18 whichcorresponding with an axis of the vessel 22.

FIGS. 10 and 11 show the lens height measuring sensor 6.

The lens height measuring sensor 6 is provided with a slide plate 40serving as a base stand. The slide plate 40 is disposed such that itsleading end side faces toward the lens support member 35, its rear endside faces toward a corner portion of the photochromic coating apparatus1, and the slide plate 40 is provided nearly on diagonals of thephotochromic coating apparatus 1 of a generally rectangular shape. Aslide block 41, which can move back and forth on the slide plate 40, isprovided on top of the slide plate 40. A sensor-mounting member 42 of aU-shape is provided on the slide block 41, and two sensors 43 and 44 aredisposed in opposite side end portions of the sensor-mounting member 42which confront each other. The sensor units 43, 44 have sensors 43 a, 44a each having a light emitting portion and a light receiving portion.The light emitting portion emits laser light, mirrors 43 b, 44 b reflectthe laser light, and the sensors 43 a, 44 a can detect the reflectedlaser light.

The sensor units 43, 44 comprise the sensors 43 a, 44 a and the mirrors43 b, 44 b disposed to be staggered and opposed. A line connecting onesensor 43 a and one mirror 43 b, and a line connecting the other sensor44 a and the other mirror 44 b are arranged at the same horizontalheight position and in parallel. The lens 10 is placed between thesensors 43 a, 44 a and the mirrors 43 b, 44 b. The sensor units 43, 44detect the presence of the lens 10 such that when the lens 10 is placedbetween the sensors 43 a, 44 a and the mirrors 43 b, 44 b, light iscrooked by the lens 10 and thereby blocked.

FIGS. 12 and 13 show the coating film uniformizing device 7.

The coating film uniformizing device 7 has a linear block 50 provided onthe base stand 2. In the linear block 50, a linear rail 51 extends inthe lateral direction of the photochromic coating apparatus 1. An X-axisservo motor 52 is mounted on one end side of the linear block 50, and anX-axis ball screw 53 journaled by bearings 54 a, 54 b is rotatablymounted on the X-axis servo motor 52. An X-axis ball nut 55 is screwedto the X-axis ball screw 53, and as the servo motor 52 is rotated, theX-axis ball nut 55 can be moved laterally. A longitudinal linear block56 erected upward is mounted on the X-axis ball nut 55.

A servo motor 57 is mounted on an upper portion of the longitudinallinear block 56, and a Z-axis ball nut 60 is screwed to a Z-axis ballscrew 59 journaled by bearings 58 a and 58 b. An elevating stage 61 ismounted on the Z-axis ball nut 60. When the servo motor 57 rotates, theelevating stage 61 can move up and down. An arm 62 extending toward thelens support member 35 is provided on the elevating stage 61, and asupport bracket 63 is provided at a leading end portion of the arm 62. Aflexible film 64, which is made of resin such as PET and aims touniformize the thickness of a film of the photochromic coating fluid, issuspended from the support bracket 63. When the elevating stage 61 ismoved in the lateral direction by driving the X-axis servo motor 52, thefilm 64 travels in a radial trajectory on the center of the lens 10.

FIG. 14 shows the UV device 8.

The UV device 8 has a main block 70 which can be raised and lowered inthe up-and-down direction by an elevating means (not shown). A UVelevating unit 71 is provided in the main block 70, and a servo motor 72is mounted on the UV elevating unit 71. A Z-axis ball nut 75 is screwedto a Z-axis ball screw 74 journaled by bearings 73 a and 73 b. A UVelevating stage 76 is mounted on the Z-axis ball nut 75. The UVelevating stage 76 moves up and down in accordance with the rotation ofthe servo motor 72. A UV light 77 to be disposed directly above the lens10 is provided on the UV elevating stage 76.

A cylinder 78 surrounding the lens 10 and comprising stainless steel isprovided below the UV light 77. A cooling pipe 79 wound in a coil isdisposed on the periphery of the cylinder 78, and cooling water cancirculate inside the cooling pipe 79. As shown in FIG. 15, gas supplyports 80 are provided in an upper portion of the cylinder 78 to becapable of introducing N₂, an inert gas, into the cylinder 78, and N₂ isdischarged to the outside of the cylinder 78 through gas discharge ports81 provided in a lower portion of the cylinder 78. A window 78 a formedfrom borosilicate glass for transmission of UV light is provided in anupper portion of the cylinder 78, as shown in FIG. 15.

FIGS. 16 and 17 show the movable fluid receiving device 9.

The movable fluid receiving device 9 has a pair of guide rails 83provided on the back of the base stand 2, and a pair of movable units 84provided at both ends of the lens support device 3 move back and forth,with the lens support device 3 being positioned therebetween. A pair ofsemicircular fluid receiving portions 85 are provided at an upperportion of the movable units 84. When the pair of fluid receivingportions 85 move forward, they are formed in an annular tubular shape toaccept the coating fluid, which falls from the lens 10, between an outertubular portion 86 and an inner tubular portion 87. The inner tubularportion 87 has an upper edge portion 85 a disposed below the outerperiphery of the lens 10.

A installing jig 88 for a temperature sensor, and a spatula fixing jig89 for preventing the adhesion of the coating fluid onto the sidesurface of the lens 10 are provided at the outer tubular portion 86. Thenumeral 90 denotes a baffle plate for blocking a clearance at thejunction between the fluid receiving portions 85.

The procedure for photochromic coating of the lens according to thepresent embodiment will be described below.

FIG. 18 is a flowchart showing a manufacturing process for aphotochromic spectacle lens.

A lens base material prepared from thiourethane resin is used as a basematerial, and cleaning of the lens 10 with an aqueous solution of analkali or by ultrasonic cleaning is performed as pretreatment.

Then, before coating with the photochromic material, the surface of thelens 10 is coated with a urethane primer to improve the adhesion of thephotochromic material. This operation is performed by linearly movingthe nozzle, which ejects the coating fluid (the urethane primer), in theradial direction of the lens from the center of the upper surface of thelens to the edge of the upper surface of the lens while rotating thelens 10. Since the coating fluid (the urethane primer) has lowviscosity, the coating fluid can be spread equally on the entire surfaceof the lens 10 by the centrifugal force of the rotated lens 10.Concretely, the rotational speed of the lens 10 during coating with thecoating fluid (the urethane primer) is about 70 rpm. After coating withthe coating fluid (the urethane primer), the lens 10 is rotated for 5seconds or so at 1,000 rpm to adjust the film thickness. The thicknessof the coating layer is, for example, 7 μm. These rotational speeds arevaried according to the gradient of the lens 10 and the temperaturearound the lens 10, thereby adjusting the film thickness to anappropriate film thickness.

After the coating layer (the primer layer) is applied, the coating layer(the primer layer) is dried (solidified) for 15 minutes at roomtemperature. The coating layer comprising the urethane primer has theproperty of becoming solid when exposed to moisture. The operationperformed up to this stage constitutes a primer coating step.

Then, the lens is subjected to a photochromic coating step. In thiscoating operation, as shown in FIG. 3, the lens 10 is set at the centerof the lens support member 35 of the photochromic coating apparatus 1.Positioning of the lens 10 is performed by a centering device (notshown). After the lens 10 is positioned in the planar direction, theheight position of the lens 10 and the edge (peripheral edge on theupper surface side of the lens) position of the lens 10 are determinedby the lens height measuring sensor 6, as shown in FIGS. 10 and 11.

Determination of the height position is performed, with the lens 10being held between the sensors 43 a, 44 a and the mirrors 43 b, 44 b ofthe sensor units 43, 44. When the lens support member 35 is raised froma lower position, laser light 43 c from one sensor 43 a located at thecenter position of the lens 10 is refracted by the lens 10. Thus, thelaser light 43 c does not reach the sensor 43 a, so that the presence ofthe lens 10 is detected. In this state, laser light 44 c from the sensor44 a of the other sensor unit 44 is reflected by the mirror 43 b andreaches the sensor 44 a, thus showing the absence of the lens 10. Whenthe lens 10 is further raised, the laser light 44 c hits the lens 10,and the laser light 44 c emitted from the sensor 44 a is blocked becauseof refraction of the laser light 44 c. Thus, the presence of the lens 10is recognized. In this manner, the center position (vertex) of the lens10 and the height of an arbitrary position of the lens 10 other than thecenter are detected.

The position of the edge, which is the marginal portion of the lens 10,can be found by knowing the height position of the center of the lens10, and detecting the gradient in the radial direction of the lens 10(the height of the lens surface) by the other sensor unit 44. That is, aknowledge of the distance between two points enables the edge positionto be calculated from the approximation expression h′=H₀D²/4L² (h′: theheight of the lens, h₀: the measured value of the height of the lens, D:the diameter of the lens, L: the distance between the sensors, normally27 mm) with reference to FIG. 19B. The shape of the lens is circular ornearly circular before cutting of the lens, so that the diameter D ofthe lens can be found without problem. In this manner, the height of thelens 43 is adjusted to an appropriate height directly below thedischarge orifice of the nozzle 24 of the coating unit 21.

After the lens 10 is positioned and its gradient is detected, a coatingoperation for the photochromic fluid is performed. As pretreatment forthe coating operation, deaeration treatment of the coating unit 21 iscarried out as shown in FIG. 8. That is, the drive motors 19 and 20 aredriven, whereby the coating unit 21 is rotated about the axis ofrotation 17 of the deaeration device 15 while being rotated about itsown inclined axis 18. In preferred embodiments, the radius of rotationof the coating unit 21 about the axis of rotation 17 is 100 to 200 mm,and the rotational speed of this rotation is 600 to 2,000 rpm, whereasthe rotational speed of the rotation of the coating unit 21 about itsown axis 18 is 0 to 300 rpm.

Because of the rotation by such deaeration treatment, the coating fluidwithin the vessel 22 presses the valve ball 25 in opposition to thepressing force of the spring 26. As a result, the coating fluid entersthe check valve 23, while air within the check valve 23 flows into thevessel 22.

It should be noted in the present invention that the deaerationtreatment is performed, with the vessel 22 being mounted with the checkvalve 23. By so doing, the check valve 23, which has not been chargedwith the coating fluid, can be charged with the coating fluid free ofair bubbles. In the check valve 23 already containing the coating fluid,the spring 26 is disposed in the check valve 23, and thus air is apt toenter between the twists of its coil. Since this air can be removed,great advantages are obtained. That is, the amount of the expensivephotochromic fluid for air purge can be decreased, and deaeration can bereliably completed in a short time. In the coating operation, the lid 23a is detached from the check valve 23, and the ejection nozzle 24 isconnected. Since the ejection nozzle 24 has not been deaerated, it isair-purged. However, its amount air-purged may be small, because itscapacity is small. Furthermore, with the ejection nozzle 24 beingconnected to the check valve 23, the ejection nozzle 24 may be lidded,and deaerated. Air purge can be done in a small amount, or can beomitted.

There is a case where stirring and deaeration are performed for thecoating fluid whose constituents have not been thoroughly uniformized.In this case, depending on the properties of the coating fluid, thecoating fluid, which has not been fully stirred or uniformized, flowsfrom the vessel 22 into the check valve 23 or the ejection nozzle 24,and is stirred and deaerated at respective sites. As a result, thecomposition of the coating fluid may be different at various sites inthe interior of the vessel 22, the check valve 23, and the ejectionnozzle 24. As a method of preventing this difference, the rotationalspeed of the drive motor 20 is decreased to reduce the revolution or theorbital motion of the vessel 22 on the revolution axis 17. With thisstate kept during the drive motor 19 is rotated to uniform the coatingfluid, it can be possible to suppress the inflow of the nonuniformcoating fluid into the check valve 23. After the coating fluid in thevessel 22 is sufficiently stirred, the rotational speed of the drivemotor 20 is increased to flow the coating fluid into the check valve 23,whereby deaeration treatment can be performed. Alternatively, thecoating fluid may be thoroughly stirred in a different container byother ordinary stirring means such as a planetary stirring deaerationdevice or an agitating blade, whereafter the coating fluid may betransferred into the vessel 22, and deaerated by the removal apparatus15 of the present invention, although this procedure requires manysteps.

By so rotating the rotating body 16 and the coating unit 21, the coatingunit 21 makes revolution on the revolution axis 17 and rotation on therotation axis 18 at the same time, thereby performing stirring anddeaeration of the coating fluid within the coating unit 21. Further, thephotochromic coating fluid having high viscosity can be uniformized.

The coating unit 21, which has finished deaeration treatment, issupported by the coating unit support device 4 shown in FIGS. 4 and 5,and the nozzle 24 of the coating unit 21 is disposed directly above thelens 10. The lens 10 is supported on the lens support member 35 whilebeing rotated (about 100 rpm). In the coating unit 21, the vessel 22 istilted to fix the nozzle 24 at the central position of the lens 10. Theplunger 27 of the coating unit 21 presses the coating fluid to open thecheck valve 23, thereby ejecting the coating fluid onto the surface ofthe lens 10 through the nozzle 24. In this ejection operation, asindicated by imaginary lines in FIG. 4, the coating unit 21 is inclinedto set the tip of the nozzle 24 at the central position of the lens 10(a position on the axis of rotation of the lens 10 and about 1 mm abovethe surface of the lens 10). In this state, the coating fluid is ejectedonto the surface of the lens 10.

Simultaneously, the film 64 of the coating film uniformizing device 7 ismoved and pressed against the lens surface. In this state, the film 64is moved in a linear trajectory from the center of the lens 10 to theedge of the lens 10. This is because the photochromic coating fluid hasgreat viscosity and does not spread under centrifugal force due to therotation of the lens 10. Thus, the coating fluid is spread to the entiresurface of the lens 10 by the rotational force of the lens 10 and thelinear movement of the film 64. The reason why the nozzle 24 is inclinedis that interference between the film 64 and the nozzle 24 is preventedby the inclination. The nozzle 24 may have the tip bent in an L-shape toavoid interference with the film 64. As described earlier, the coatingunit is rotated beforehand on the revolution axis 17 and is rotated onthe rotation axis 18 to carry out deaeration. Thus, no air bubbles arecontained in the coating fluid, and the whole of the coating fluid isrendered uniform, so that a uniform coating film free from air bubblesand film thickness irregularities can be obtained.

At this stage, the amount of the photochromic coating fluid on the lens10 is larger than the film thickness of the desired photochromic film,thus making it necessary to remove the surplus coating fluid on the lens10 until the desired amount of the fluid is attained. Thus, an operationfor rotating the lens 10 to spin off the coating fluid on the lens 10 isperformed. The rotational speed of the lens 10 is determined byconditions conformed to the temperature inside the apparatus and thegradient of the lens 10. For example, the lens 10 is spun at 600 rpm.

Then, the lens 10 is surrounded by the cylinder 78 of the UV device 78,and the interior of the cylinder 10 is purged with nitrogen. The reasonfor providing a nitrogen atmosphere is that in the presence of oxygen,the coating film minimally cures. The UV lamp 77 is brought to anappropriate height position, and the coating film is cured by the UVlamp 77. The window 78 a installed between the UV lamp 77 and the lens10 allows UV light to be transmitted into the cylinder 78, and alsoplays the role of a filter for screening out light of a wavelength inthe vicinity of 300 nm or shorter.

The reason for cutting off the wavelength in the vicinity of 300 nm orshorter is that depending on the type of the photochromic coating fluid,the coating film is wrinkled, and a uniform film is not obtained. Thereason why borosilicate glass is used as the material is that thismaterial is heat-resistant and does not break under heat of the UV lamp.

After completion of photochromic coating, the photochromic coating layeris inspected for the state of adhesion. The coating layer poorly adheredis rejected, and a good product is subjected to annealing treatment.This treatment is heat treatment performed for 1 hour at 110° C.

In this manner, the photochromic coating layer is formed on the lens 10.This coating layer is the one obtained after air is removed by theremoval apparatus 15, and the coating fluid is deaerated and stirred notonly in the vessel 22, but also in the check valve 23 (or, alsoincluding the ejection nozzle 24). Thus, the coating unit 21 as a wholeensures coating with a uniform coating fluid free from concentrationunevenness. Consequently, a high quality photochromic lens can beproduced.

The embodiment of the present invention has been described above, butneedless to say, various modifications or changes of the presentinvention are possible based on the technical ideas of the presentinvention.

For example, in connection with the sensor units 43, 44, the lineconnecting the sensor 43 a and the mirror 43 b is located at the samehorizontal height position as the line connecting the other sensor 44 aand the other mirror 44 b, but one of the sensors may be located at adifferent height position to provide a height difference between the twosensors. In this case, the edge position of the lens 10 is determined inconsideration of the height difference between the sensors.

According to the embodiment of the present invention, photochromiccoating is taken as an example. However, the present invention can beapplied to other coating technologies.

The spectacle lens having a convex surface and a concave surface hasbeen coated, but the present invention can be applied to coating ofglass having flat surfaces.

The removal method for entrained air according to the present inventioncomprising the steps of:

(A) preparing a coating unit comprising a cylindrical vessel storing thecoating fluid and a check valve for preventing back-flow of the coatingfluid connecting with the vessel;

(B) plugging an outlet of the coating fluid existing downstream of thecheck valve; and

(C) rotating the coating unit on an axis of the vessel and orbiting thecoating unit on a revolution axis simultaneously whereby introducing thecoating fluid into the check valve, discharging air inside the checkvalve toward the vessel, and further removing air incorporated in thecoating fluid from the coating fluid. By thus removing air incorporatedin the check valve, air bubbles are not contained in the coating layer,and a uniform layer free from film thickness unevenness can be obtained.Nor is it necessary to perform air purge with the coating fluid, as doneconventionally, so that a saving in the coating fluid can be made. Theuse of the check valve makes it possible to prevent fluid drip of thecoating fluid, and form a stable coating film.

In the above removal method for entrained air, the coating unit preparedin the step (A) can further contain an ejection nozzle for ejecting thecoating fluid connecting with the check valve and the plugging in thestep (B) can be carried out by plugging an outlet of the ejectionnozzle. Thus, entrained air in the ejection nozzle can also be removed,and a more stable coating film can be formed.

In the above removal method for entrained air wherein a rotational speedof revolution of the coating unit is set such that the speed in a latestage of a rotating operation is rendered higher than the speed in anearly stage of the rotating operation, if stirring of the respectivecomponents of the coating fluid is not sufficient, or if the propertiesof the coating fluid render stirring difficult, the coating fluid can bestirred sufficiently, and the coating fluid can be uniformized.

Further, the coating fluid used in the above invention is a photochromiccoating fluid to be coated on the surface of spectacles. Thus, aphotochromic coating film of good quality can be formed on the surfaceof spectacles.

The removal apparatus for entrained air according to the presentinvention comprises a casing which can rotate on a rotation axis andalso can orbit on revolution axis, and a coating unit comprising acylindrical vessel accommodating a coating fluid inside, a check valvefor preventing back-flow of the coating fluid connecting the vessel anda lid for plugging an outlet of the coating fluid existing downstream ofthe check valve; wherein the rotation axis being located, with respectto the revolution axis, outwardly and downwardly in a circumferentialdirection of an orbital on the revolution axis, the coating unit beingsupported by the casing detachably such that the lid of the coating unitis located below, and the coating unit being rotated on the rotationaxis and being orbit on the revolution axis simultaneously with thecasing, to deaerate air contained in the coating fluid. Thus, airbubbles are not contained in the coating layer, and a uniform layer freefrom film thickness unevenness can be obtained by using the apparatus.Nor is it necessary to perform air purge with the coating fluid, as doneconventionally, so that a saving in the coating fluid can be made.

When the lid on the check valve is detached, the ejection nozzle isconnected to the check valve, and then a lid is mounted on a tip portionof the ejection nozzle, it is possible to remove entrained air in theejection nozzle and to form a more stable coating film.

In the removal apparatus for entrained air according to the presentinvention, the coating fluid is a photochromic coating fluid to becoated on the surface of spectacles. Thus, a photochromic coating filmof good quality can be formed on the surface of spectacles.

In the removal apparatus for entrained air, the flange facing outward isformed on the vessel, and the flange is detachably mounted on thecasing. Thus, the vessel can be fixed easily and reliably, and thevessel can be rotated stably.

1. A method for removing air from a coating fluid containing entrainedair comprising the steps of: (A) preparing a coating unit comprising acylindrical vessel storing the coating fluid and a check valve forpreventing back-flow of the coating fluid connecting with the vessel;(B) plugging an outlet of the coating fluid existing downstream of thecheck valve; and (C) rotating the coating unit on an axis of the vesseland orbiting the coating unit on a revolution axis simultaneouslywhereby introducing the coating fluid into the check valve, dischargingair resided inside of the check valve toward the vessel, and furtherremoving air incorporated in the coating fluid from the coating fluid.2. The method according to claim 1, wherein the coating unit prepared inthe step (A) further contains an ejection nozzle for ejecting thecoating fluid connecting with the check valve, the plugging in the step(B) is carried out by plugging an outlet of the ejection nozzle, and thecoating fluid is introduced into the check valve and the ejectionnozzle, and the air inside the check valve and the air inside theejection nozzle are discharged toward the vessel in the step (C).
 3. Themethod according to claim 1, wherein a rotational speed of revolution ofthe coating unit is set such that the speed in a late stage of arotating operation is rendered higher than the speed in an early stageof the rotating operation.
 4. The method according to claim 1, whereinthe coating fluid is a photochromic coating fluid to be coated on asurface of spectacles.
 5. A removal apparatus for entrained air in acoating fluid, the apparatus comprises a casing which can rotate on arotation axis and also can orbit on revolution axis, and a coating unitcomprising a cylindrical vessel accommodating a coating fluid inside, acheck valve for preventing back-flow of the coating fluid connecting thevessel and a lid for plugging an outlet of the coating fluid existingdownstream of the check valve; wherein the rotation axis being located,with respect to the revolution axis, outwardly and downwardly in acircumferential direction of an orbital on the revolution axis, thecoating unit being supported by the casing detachably such that the lidof the coating unit is located below, and the coating unit being rotatedon the rotation axis and being orbit on the revolution axissimultaneously with the casing, to discharge air resided inside of thecheck valve toward the vessel, and further to remove air incorporated inthe coating fluid.
 6. The removal apparatus for entrained air in acoating fluid according to claim 5, wherein the coating unit furthercontains an ejection nozzle for ejecting the coating fluid connectingwith the check valve, and the lid is mounted on a tip portion of theejection nozzle.
 7. The removal apparatus for entrained air in a coatingfluid according to claim 5, wherein the coating fluid is a photochromiccoating fluid to be coated on a surface of spectacles.
 8. The removalapparatus for entrained air in a coating fluid according to claim 5,wherein a flange facing outward is formed on a periphery of the vessel,and the flange is detachably mounted on the casing.